In-line measuring device

ABSTRACT

An inline measuring device includes a vibration-type measurement pickup having at least one measuring tube, which has a medium to be measured flowing through it during operation. The measuring tube is made by means of an exciter arrangement to execute, at least at times and/or at least in part, lateral oscillations and, at least at times and/or at least in part, torsional oscillations about an imaginary measuring tube longitudinal axis. The torsional oscillations alternate with the lateral oscillations or are, at times, superimposed thereon. Also included is a sensor arrangement for producing oscillation measurement signals correspondingly representing oscillations of the measuring tube. Measuring device electronics controlling the exciter arrangement generates, by means of at least one of the oscillation measurement signals and/or by means of the exciter current, at least at times, at least one measured value, which represents the at least one physical quantity to be measured. Additionally, the measuring device electronics also determines a first intermediate value, which corresponds to the lateral current component of the exciter current serving to maintain the lateral oscillations of the measuring tube and/or to a damping of the lateral oscillations of the measuring tube, as well as a second intermediate value, which corresponds to a torsional current component of the exciter current serving to maintain the torsional oscillations of the measuring tube and/or to a damping of the torsional oscillations of the measuring tube. With the goal of producing the measured value at high accuracy, such value is determined also taking into consideration these two intermediate values. The measured value obtained in this way is distinguished especially by high accuracy also in the case of media of two, or more, phases.

This application is a Continuation of U.S. patent application Ser. No.11/084,527 filed on Mar. 21, 2005, which is a nonprovisional applicationof U.S. Provisional Appl. 60/570,490 filed on May 13, 2004 and U.S.Provisional Appl. 60/556,491 filed on Mar. 26, 2004.

FIELD OF THE INVENTION

The invention relates to an inline measuring device having avibratory-type measurement pickup, especially a Coriolismass-flow/density measuring device for a medium, especially a two, ormore, phase medium flowing in a pipeline, as well as a method forproducing by means of such a measurement pickup a measured valuerepresenting a physical, measured quantity of the medium, for example amass flow rate, a density and/or a viscosity.

BACKGROUND OF THE INVENTION

In the technology of process measurements and automation, themeasurement of physical parameters of a medium flowing in a pipeline,parameters such as e.g. the mass flow rate, density and/or viscosity,such inline measuring devices, especially Coriolis mass flow measuringdevices, are used, which bring about reaction forces in the medium, suchas e.g. Coriolis forces corresponding to the mass flow rate, inertialforces corresponding to the density, or frictional forces correspondingto the viscosity, etc., by means of a vibratory measurement pickupinserted into the course of the pipeline carrying the medium andtraversed during operation by the medium, and by means of a measurementand operating circuit connected therewith. Derived from these reactionforces, the measuring devices then produce a measurement signalrepresenting the particular mass flow rate, the particular viscosityand/or the particular density of the medium. Inline measuring devices ofthis type, utilizing a vibratory measurement pickup, as well as theirmanner of operation, are known per se to those skilled in the art andare described in detail in e.g. WO-A 03/095950, WO-A 03/095949, WO-A03/076880, WO-A 02/37063, WO-A 01/33174, WO-A 00/57141, WO-A 99/39164,WO-A 98/07009, WO-A 95/16897, WO-A 88/03261, US 2003/0208325, U.S. Pat.No. 6,691,583, U.S. Pat. No. 66 51 51 13, U.S. Pat. No. 6,513,393, U.S.Pat. No. 6,505,519, U.S. Pat. No. 6,006,609, U.S. Pat. No. 5,869,770,U.S. Pat. No. 5,796,011, U.S. Pat. No. 5,616,868, U.S. Pat. No.5,602,346, U.S. Pat. No. 5,602,345, U.S. Pat. No. 5,531,126, U.S. Pat.No. 5,301,557, U.S. Pat. No. 5,253,533, U.S. Pat. No. 5,218,873, U.S.Pat. No. 5,069,074, U.S. Pat. No. 4,876,898, U.S. Pat. No. 4,733,569,U.S. Pat. No. 4,660,421, U.S. Pat. No. 4,524,610, U.S. Pat. No.4,491,025, U.S. Pat. No. 4,187,721, EP-A 1 291 639, EP-A 1 281 938, EP-A1 001 254 or EP-A 553 939.

For guiding the medium, the measurement pickups include at least onemeasuring tube with a straight tube segment held in a, for example,tubular or box-shaped, support frame. For producing the above-mentionedreaction forces during operation, the tube segment is caused to vibrate,driven by an electromechanical exciter arrangement. For registeringvibrations of the tube segment, particularly at its inlet and outletends, the measurement pickups additionally include an electrophysicalsensor arrangement reacting to movements of the tube segment.

In the case of Coriolis mass flow measuring devices, the measurement ofthe mass flow rate of a medium flowing in a pipeline rests, for example,on having the medium flow through the measuring tube inserted into thepipeline and oscillating during operation laterally to a measuring tubeaxis, whereby Coriolis forces are induced in the medium. These, in turn,effect that the inlet and outlet end regions of the measuring tubeoscillate shifted in phase relative to one another. The magnitude ofthis phase shift serves as a measure of the mass flow rate. Theoscillations of the measuring tube are, to this end, registered by meansof two oscillation sensors of the above-mentioned sensor arrangementseparated from one another along the length of the measuring tube andare transformed into oscillation measurement signals, from whose phaseshift relative to one another the mass flow rate is derived.

Already the above-mentioned U.S. Pat. No. 4,187,721 mentions, further,that the instantaneous density of the flowing medium can also bemeasured by means of such inline measuring devices, and, indeed, on thebasis of a frequency of at least one of the oscillation measurementsignals delivered from the sensor arrangement. Moreover, usually also atemperature of the medium is directly measured in suitable manner, forexample by means of a temperature sensor arranged on the measuring tube.Additionally, straight measuring tubes can, as is known, upon beingexcited to torsional oscillations about a torsional oscillation axisextending essentially parallel to, or coinciding with, the longitudinalaxis of the measuring tube, effect that radial shearing forces areproduced in the medium as it flows through the tube, whereby significantoscillation energy is withdrawn from the torsional oscillations anddissipated in the medium. As a result of this, a considerable damping ofthe torsional oscillations of the oscillating measuring tube occurs, sothat, additionally, electrical exciting power must be added, in order tomaintain the torsional oscillations. On the basis of the electricalexciting power required to maintain the torsional oscillations of themeasuring tube, the measurement pickup can also be used to determine, atleast approximately, a viscosity of the medium; compare, in thisconnection also U.S. Pat. No. 4,524,610, U.S. Pat. No. 5,253,533, U.S.Pat. No. 6,006,609 or U.S. Pat. No. 6,651,513. It can, consequently,assumed, without more in the following, that, even when not expresslystated, modern inline measuring devices using a vibratory measurementpickup, especially Coriolis mass flow measuring devices, have theability to measure, in any case, also density, viscosity and/ortemperature of the medium, especially since these are always neededanyway in the measurement of mass flow rate for the compensation ofmeasurement errors arising from fluctuating density and/or viscosity ofthe medium; compare, in this connection, especially the alreadymentioned U.S. Pat. No. 6,513,393, U.S. Pat. No. 6,006,609, U.S. Pat.No. 5,602,346, WO-A 02/37063, WO-A 99/39164 or also WO-A 00/36379.

In the application of inline measuring devices using a vibratorymeasurement-pickup, it has, however, become evident, as also discussed,for example, in JP-A 10-281846, WO-A 03/076880, EP-A 1 291 639, U.S.Pat. No. 6,505,519 or U.S. Pat. No. 4,524,610, that, in the case ofinhomogeneous media, especially two, or more, phase media, theoscillation measurement signals derived from the oscillations of themeasuring tube, especially also the mentioned phase shift, can besubject to fluctuations to a considerable degree and, thus, in somecases, can be completely unusable for the measurement of the desiredphysical parameters, without the use of auxiliary measures, this inspite of keeping the viscosity and density in the individual phases ofthe medium, as well as also the mass flow rate, practically constantand/or appropriately taking them into consideration. Such inhomogeneousmedia can, for example, be liquids, into which, as is e.g. practicallyunavoidable in dosing or bottling processes, a gas, especially air,present in the pipeline is entrained or out of which a dissolved medium,e.g. carbon dioxide, outgasses and leads to foam formation. As otherexamples of such inhomogeneous media, emulsions and wet, or saturated,steam can be named. As causes for the fluctuations arising in themeasurement of inhomogeneous media by means of vibratory measurementpickups, the following can be noted by way of example: the unilateralclinging or deposit of gas bubbles or solid particles, entrained inliquids, internally on the measuring tube wall, and the so-called“bubble-effect”, where gas bubbles entrained in the liquid act as flowbodies for liquid volumes accelerated transversely to the longitudinalaxis of the measuring tube.

While, for decreasing the measurement errors associated with two, ormore, phase media, a flow, respectively medium, conditioning precedingthe actual flow rate measurement is proposed in WO-A 03/076880, bothJP-A 10-281846 and U.S. Pat. No. 6,505,519, for example, describe acorrection of the flow rate measurement, especially the mass flow ratemeasurement, based on the oscillation measurement signals, whichcorrection rests especially on the evaluation of deficits between ahighly accurately measured, actual medium density and an apparent mediumdensity determined by means of Coriolis mass flow measuring devicesduring operation.

In particular, pre-trained, in some cases even adaptive, classifiers ofthe oscillation measurement signals are proposed for this. Theclassifiers can, for example, be designed as a Kohonen map or neuralnetwork, and the correction is made either on the basis of some fewparameters, especially the mass flow rate and the density measuredduring operation, as well as other features derived therefrom, or alsousing an interval of the oscillation measurement signals encompassingone or more oscillation periods. The use of such a classifier brings,for example, the advantage that, in comparison to conventional Coriolismass flow/density meters, no, or only very slight, changes have to bemade at the measurement pickup, in terms of mechanical construction, theexciter arrangement or the operating circuit driving such, which arespecially adapted for the particular application. However, aconsiderable disadvantage of such classifiers includes, among others,that, in comparison to conventional Coriolis mass flow measuringdevices, considerable changes are required in the area of the measuredvalue production, above all with regards to the analog-to-digitaltransducer being used and the microprocessors. As, namely, alsodescribed in U.S. Pat. No. 6,505,519, required for such a signalevaluation, for example, in the digitizing of the oscillationmeasurement signals, which can exhibit an oscillation frequency of about80 Hz, is a sampling rate of about 55 kHz or more, in order to obtain asufficient accuracy. Stated differently, the oscillation measurementsignals have to be samples with a sampling ratio of far above 600:1.Beyond this, also the firmware stored and executed in the digitalmeasurement circuit is correspondingly complex. A further disadvantageof such classifiers is that they must be trained and correspondinglyvalidated for the conditions of measurement actually existing duringoperation of the measurement pickup, be it regarding the particulars ofthe installation, the medium to be measured and its usually variableproperties, or other factors influencing the accuracy of measurement.Because of the high complexity of the interplay of all these factors,the training and its validation can occur ultimately only on site andindividually for each measurement pickup, this in turn meaning aconsiderable effort for the startup of the measurement pickup. Finally,it has been found, that such classifier algorithms, on the one handbecause of the high complexity, on the other because of the fact thatusually a corresponding physical-mathematical model with technicallyrelevant or comprehensible parameters is not explicitly present, exhibita very low transparency and are, consequently, often difficult toexplain. Accompanying this situation, it is clear that considerablereservations can occur on the part of the customer, with such acceptanceproblems especially arising when the classifier, additionally, isself-adapting, for example a neural network.

As a further possibility for getting around the problem of inhomogeneousmedia, it is proposed, for instance, already in U.S. Pat. No. 4,524,610to install the measurement pickup such that the straight measuring tubeextends essentially vertically, in order to prevent, as much aspossible, a deposition of such disturbing, especially gaseous,inhomogeneities. Here, however, one is dealing with a very specialsolution which cannot always be implemented, without more, in thetechnology of industrial process measurement. On the one hand, in thiscase, it can happen, namely, that the pipeline, into which themeasurement pickup is to be inserted, might have to be adapted to themeasurement pickup, rather than the reverse, which can mean an increasedexpense for implementing the measurement location. On the other hand, asalready mentioned, the measuring tubes might have a curved shape, inwhich case the problem cannot always be solved satisfactorily by anadapting of the installation orientation anyway. It has, moreover, beenfound in this case that the aforementioned corruptions of themeasurement signal are not necessarily prevented with certainty by theuse of a vertically installed, straight measuring tube anyway.

SUMMARY OF THE INVENTION

An object of the invention is, therefore, to provide a correspondinginline measuring device, especially a Coriolis mass flow measuringdevice, that is suited for measuring a physical, measured quantity,especially mass flow rate, density and/or viscosity, very accurately,even in the case of inhomogeneous, especially two, or more, phase media,and, indeed, especially desirably with a measurement error of less than10% referenced to the actual value of the measured quantity. A furtherobject is to provide a corresponding method for producing acorresponding measured value.

For achieving this object, the invention resides in an inline measuringdevice, especially a Coriolis mass flow rate/density measuring deviceand/or a viscosity measuring device, for measuring at least onephysical, measured quantity, especially a mass flow rate, a densityand/or a viscosity, of a medium, especially a two, or more, phasemedium, conducted in a pipeline. The inline measuring device includesfor this purpose a vibratory measurement pickup and a measuring deviceelectronics electrically coupled with the measurement pickup. Themeasurement pickup includes, inserted into the course of the pipeline, ameasuring tube, especially an essentially straight measuring tube, thuscommunicating with the pipeline and serving to conduct the medium to bemeasured, an exciter arrangement acting on the measuring tube forcausing the at least one measuring tube to vibrate, and a sensorarrangement for registering vibrations of the at least one measuringtube and delivering at least one oscillation measurement signalrepresenting oscillations of the measuring tube. The exciter arrangementcauses the measuring tube, during operation, at least at times and/or atleast partially, to vibrate with lateral oscillations, especiallybending oscillations. Additionally, the exciter arrangement causes themeasuring tube, during operation, at least at times and/or at leastpartially, to vibrate with torsional oscillations about an imaginary,measuring tube longitudinal axis essentially aligned with the measuringtube, especially an axis developed as a principal axis of inertia of themeasuring tube. The torsional oscillations are especially ones whichalternate with the lateral oscillations or are at times superimposedthereon. The measuring device electronics delivers, at least at times,an exciting current driving the exciter arrangement. Further, themeasuring device electronics determines a first intermediate value,which corresponds to a lateral current component of the exciter currentserving for maintaining the lateral oscillations of the measuring tubeand/or to a damping of the lateral oscillations of the exciter current.Additionally, the measuring device electronics determines a secondintermediate value, which corresponds to a torsional current componentof the exciter current serving for maintaining the torsionaloscillations of the measuring tube and/or to a damping of the torsionaloscillations of the measuring tube. By means of the at least oneoscillation measurement signal and/or by means of the exciter current,as well as with application of the first and second intermediate values,the measuring device electronics generates, at least at times, at leastone measured value, which represents the at least one physical quantitybeing measured, especially the mass flow rate, the density or theviscosity of the medium.

Additionally, the invention resides in a method for measuring aphysical, measured quantity, especially mass flow rate, a density and/ora viscosity, of a medium flowing in a pipeline, especially a two, ormore, phase medium, by means of an inline measuring device having avibratory measurement pickup, especially a Coriolis mass flow measuringdevice, and a measuring device electronics electrically coupled with thepickup, which method comprises the following steps:

-   -   allowing a medium to be measured to flow through at least one        measuring tube of the measurement pickup communicating with the        pipeline and feeding an exciter current into an exciter        arrangement mechanically coupled with the measuring tube guiding        the medium, in order to cause the measuring tube to execute        mechanical oscillations,    -   effecting lateral oscillations, especially bending oscillations,        of the measuring tube and effecting torsional oscillations of        the measuring tube, especially torsional oscillations        superimposed on the lateral oscillations,    -   registering vibrations of the measuring tube and producing at        least one oscillation measurement signal representing        oscillations of the measuring tube,    -   determining a first intermediate value derived from the exciter        current and corresponding to a lateral current component of the        exciter current serving for maintaining the lateral oscillations        of the measuring tube and/or to a damping of the lateral        oscillations of the measuring tube,    -   determining a second intermediate value derived from the exciter        current and corresponding to a torsional current component of        the exciter current serving for maintaining the torsional        oscillations of the measuring tube and/or to a damping of the        torsional oscillations of the measuring tube, and    -   using the at least one oscillation measurement signal and/or the        exciter current, as well as the first and second intermediate        values, for producing a measured value representing the physical        quantity to be measured.

According to a first embodiment of the inline measuring device of theinvention, the measuring electronics determines, derived from the atleast one oscillation measurement signal and/or from the excitercurrent, an initial measured value, which corresponds, at leastapproximately, to the at least one quantity to be measured, and, on thebasis of the first and second intermediate values, a correction valuefor the initial measured value, and the measuring device electronicsgenerates the measured value by means of the initial measured value andthe correction value.

In a second embodiment of the inline measuring device of the invention,the measuring tube, driven by the exciter arrangement, executestorsional oscillations having a measuring tube torsional oscillationfrequency which is set to be different from a measuring tube bendingoscillation frequency with which the measuring tube, driven by theexciter arrangement, executes lateral oscillations.

According to a third embodiment of the inline measuring device of theinvention, the measuring tube communicates with the connected pipelinevia an inlet tube piece opening into an inlet end and via an outlet tubepiece opening into an outlet end, and the measurement pickup includes acounteroscillator fixed to the inlet end and to the outlet end of themeasuring tube, especially also mechanically coupled with the exciterarrangement, and vibrating, at least at times, during operation,especially with phase opposite to that of the measuring tube.

In a fourth embodiment of the inline measuring device of the invention,the measuring device electronics determines the correction value on thebasis of a comparison of the first intermediate value with the secondintermediate value and/or on the basis of a difference existing betweenthe first intermediate value and the second intermediate value.

According to a fifth embodiment of the inline measuring device of theinvention, the measuring device electronics produces the first and/orthe second intermediate value also on the basis of the least oneoscillation measurement signal.

In a sixth embodiment of the inline measuring device of the invention,the at least one measured value represents a viscosity of the mediumflowing in the measuring tube, and the measuring device electronicsdetermines also the initial measured value on the basis of the excitercurrent, and/or a component of the exciter current, driving the exciterarrangement.

According to a seventh embodiment of the inline measuring device of theinvention, the at least one measured value represents a density of themedium flowing in the measuring tube, and the measuring tube electronicsdetermines the initial measured value using the at least one oscillationmeasurement signal and/or the exciter current by recognizing that thiscorresponds to the density to be measured and/or to an oscillationfrequency of the at least one oscillation measurement signal.

In an eighth embodiment of the inline measurement device of theinvention, the measuring device electronics determines at least attimes, on the basis of the first and second intermediate values, aconcentration measured value, which represents an, especially relative,volume and/or mass fraction of a phase of the medium, in the case of atwo, or more, phase medium in the measuring tube.

According to a ninth embodiment of the inline measuring device of theinvention, the sensor arrangement delivers at least one oscillationmeasurement signal representing, at least in part, inlet end lateraloscillations, especially bending oscillations, of the measuring tube,and at least one second oscillation measurement signal representing, atleast in part, outlet end lateral oscillations, especially bendingoscillations, of the measuring tube.

In a tenth embodiment of the inline measuring device of the invention,the at least one measured value represents a mass flow rate of themedium flowing in the measuring tube, and the measuring deviceelectronics determines the initial measured value using the twooscillation measurement signals by recognizing that this corresponds tothe mass flow rate to be measured and/or to a phase difference betweenthe two oscillation measurement signals.

According to a first embodiment of the method of the invention, the stepof producing the measured value includes the steps of:

-   -   developing, using the at least one oscillation measurement        signal and/or the exciter current, an initial measured value        corresponding at least approximately to the physical quantity to        be measured,    -   producing a correction value for the initial value by means of        the first and second intermediate values, and    -   correcting the initial measured value by means of the correction        value, for producing the measured value.

In a second embodiment of the method of the invention, the step ofproducing the correction value for the initial measurement valuecomprises the steps of:

-   -   Comparing the first intermediate value with the second        intermediate value for determining a difference existing between        the two intermediate values and    -   determining, taking into consideration the difference existing        between the two intermediate values, a concentration measured        value, which represents, in the case of a two, or more, phase        medium in the measuring tube, an, especially relative, volume        and/or mass fraction of a medium phase.

A basic idea of the invention resides in operating the measurementpickup in a dual-mode for the purpose of correcting or compensatingpossible measurement errors caused especially by inhomogeneities in themedium to be measured. In the dual mode, the measuring tube is caused tovibrate alternately in at least two oscillation modes which areessentially independent of one another, namely a lateral oscillationmode and a torsional oscillation mode. On the basis of operatingparameters of the measurement pickup determined during the dual-modeoperation, especially the exciter current, the frequencies and/oramplitudes of the oscillations of the measuring tube, etc., required formaintaining the lateral and torsional oscillations of the measuringtube, very exact and amazingly robust correction values for the actualmeasured values can be determined in a very simple manner.

The invention rests, in this connection, especially on the discoverythat the exciter power fed into the measurement pickup for maintainingthe lateral oscillations of the measuring tube can be affected to a highdegree by inhomogeneities in the medium being measured, inhomogeneitiessuch as e.g. entrained gas bubbles or solid particles, etc. Incomparison therewith, the exciter power fed into the measurement pickupfor maintaining torsional oscillations of the measuring tube depend to aconsiderably lesser extent on such inhomogeneities, so that, duringoperation, based on this exciter power, especially based on the excitercurrent component actually fed for maintaining the torsionaloscillations, up-to-the-moment reference values can be determined, withwhose help a comparison of the correspondingly determined measuredvalues for the lateral oscillations, for example the exciter currentcomponent actually fed for maintaining the lateral oscillations, can bemade. On the basis of this, for example, normalized or subtractivelyexecuted comparison, an instantaneous degree of inhomogeneity in themedium can be estimated and, derived from this, a sufficiently accurateconclusion made as to the measurement error which has entered themeasurement. The inline measuring device of the invention is, therefore,especially suited for the measurement of a physical, measured quantity,especially a mass flow rate, a density and/or a viscosity, even of atwo, or more, phase medium flowing in a pipeline, especially aliquid-gas mixture.

An advantage of the invention is that the correction values to bedetermined are well reproducible over a large range of application and,also, the forming rules for determining the correction values duringmeasurement operation can be formulated relatively simply. Moreover,these forming rules can be calculated initially with a relatively smalleffort. A further advantage of the invention is, additionally, to beseen in the fact that, in the case of the inline measuring device of theinvention, as compared to a conventional type, especially such asdescribed in WO-A 03/095950, WO-A 03/095949 or U.S. Pat. No. 4,524,610,only in the case of the usually digital, measured value production doslight changes have to be made, these being essentially limited to thefirmware, while, both in the case of the measurement pickup and in theproduction and preprocessing of the oscillation measurement signals, no,or only slight, changes are required. Thus, for example, even in thecase of two, or more, media, the oscillation measurement signals can besampled, as before, with a usual sampling ratio of far under 100:1,especially of about 10:1.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and further advantageous embodiments will now be explainedin detail on the basis of examples of embodiments presented in thefigures of the drawing. Equal parts are provided in all figures withequal reference characters; when required in the interest of clarity,already mentioned reference characters are omitted in subsequentfigures.

FIG. 1 shows an inline measuring device which can be inserted into apipeline for measuring a mass flow rate of a fluid guided in thepipeline,

FIG. 2 shows, in a perspective, side view, an example of an embodimentfor a measurement pickup suited for the measuring device of FIG. 1,

FIG. 3 shows, sectioned in a side view, the measurement pickup of FIG.2,

FIG. 4 shows the measurement pickup of FIG. 2 in a first cross section,

FIG. 5 shows the measurement pickup of FIG. 2 in a second cross section,

FIG. 6 shows, sectioned in a side view, a further example of anembodiment of a vibratory measurement-pickup suited for the inlinemeasuring device of FIG. 1,

FIG. 7 shows schematically in the form of a block diagram a preferredembodiment of a measuring device electronics suited for the inlinemeasuring device of FIG. 1, and

FIGS. 8 and 9 show, graphically, measurement data experimentallydetermined using an inline measuring device of the FIGS. 1 to 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows, perspectively, an inline measuring device 1 suited forregistering a physical, measured quantity, e.g. a mass flow rate m, adensity ρ and/or a viscosity η, of a medium flowing in a pipeline (notshown) and for imaging this measured quantity in an instantaneouslyrepresenting, measured value X_(X). The medium in this instance can bepractically any flowable substance, for example a liquid, a gas, avapor, or the like.

The inline measuring device 1, for example provided in the form of aCoriolis mass flow, density and/or viscosity meter, includes therefor avibratory measurement pickup 10 flowed-through by the medium to bemeasured, an example of an embodiment and developments being shown inFIGS. 2 to 6, together with a measuring device electronics 50, asillustrated schematically in FIGS. 2 and 7. Preferably, the measuringdevice electronics 50 is, additionally, so designed that it can, duringoperation of the inline measuring device 1, exchange measurement and/oroperational data with a measured value processing unit superordinated,i.e. located at a higher level, with respect thereto, for example aprogrammable logic controller (PLC), a personal computer and/or aworkstation, via a data transmission system, for example a field bussystem. Furthermore, the measuring device electronics is designed suchthat it can be supplied from an external energy supply, for example alsoover the aforementioned field bus system. For the case in which thevibratory measuring device is provided for coupling to a field bus orsome other communication system, the, especially programmable, measuringdevice electronics 50 is equipped with a corresponding communicationsinterface for a communication of data, e.g. for the transmission of themeasurement data to the already mentioned, programmable logic controlleror to a superordinated process control system. For accommodation of themeasuring device electronics 50, an electronics housing 200 isadditionally provided, especially one mounted externally directly ontothe measurement pickup 10, but even one possibly set apart from such.

As already mentioned, the inline measuring device includes a vibratorymeasurement pickup, which is flowed-through by the medium to bemeasured, and which serves for producing, in a through-flowing medium,mechanical reaction forces, especially Coriolis forces, dependent on themass flow rate, inertial forces dependent on the density of the mediumand/or frictional forces dependent on the viscosity of the medium,forces which react measurably, i.e. capable of being detected by sensor,on the measurement pickup. Derived from these reaction forcescharacterizing the medium, e.g. the mass flow rate, the density and/orthe viscosity of the medium can be measured in manner known to thoseskilled in the art. In FIGS. 3 and 4, an example of an embodiment of anelectrophysical transducer arrangement, serving as a vibratorymeasurement pickup 10, is schematically illustrated. The mechanicalconstruction and manner of functioning of such a transducer arrangementis known per se to those skilled in the art and is also described indetail in U.S. Pat. No. 6,691,583, WO-A 03/095949 or WO-A 03/095950.

For guiding the medium and for producing said reaction forces, themeasurement pickup includes at least one, essentially straight,measuring tube 10 of predeterminable measuring tube diameter. Measuringtube 10 is caused, during operation, to vibrate, at least at times, andis repeatedly elastically deformed thereby. Elastic deformation of themeasuring tube lumen means here, that a spatial form and/or a spatialposition of the measuring tube lumen is changed within an elastic rangeof the measuring tube 10 in predeterminable manner cyclically,especially periodically; compare, in this connection, also U.S. Pat. No.4,801,897, U.S. Pat. No. 5,648,616, U.S. Pat. No. 5,796,011, U.S. Pat.No. 6,006,609, U.S. Pat. No. 6,691,583, WO-A 03/095949 and/or WO-A03/095950. It should be mentioned here that, instead of the measurementpickup shown in the example of an embodiment having a single, straightmeasuring tube, the measurement pickup serving for implementation of theinvention can, as well, be selected from a multiplicity of vibratorymeasurement pickups known in the state of the art. In particular,suited, for example, are vibratory measurement pickups having twoparallel, straight measuring tubes flowed-through by the medium to bemeasured, such as are described in detail also in U.S. Pat. No.5,602,345.

As shown in FIG. 1, the measurement pickup 1 additionally has ameasurement pickup housing 100 surrounding the measuring tube 10, aswell as surrounding possible other components of the measurement pickup(see also further below). Housing 100 acts to protect tube 10 and othercomponents from damaging environmental influences and/or to damppossible outwardly-directed sound emissions of the measurement pickup.Beyond this, the measurement pickup housing 100 also serves as amounting platform for an electronics housing 200 housing the measuringdevice electronics 50. To this end, the measurement pickup housing 100is provided with a neck-like transition piece, on which the electronicshousing 200 is appropriately fixed; compare FIG. 1. Instead of thetube-shaped transducer housing 100 shown here extending coaxially withthe measuring tube, other suitable housing forms can, of course, beused, such as e.g. box-shaped structures.

The measuring tube 10, which communicates in the usual manner at inletand outlet ends with the pipeline introducing, respectively extracting,the medium to be measured, is oscillatably suspended in the preferablyrigid, especially bending- and twisting-stiff, transducer housing 100.For permitting the medium to flow through, the measuring tube isconnected to the pipeline via an inlet tube piece 11 opening into theinlet end 11# and an outlet tube piece 12 opening into the outlet end12#. Measuring tube 10, inlet tube piece 11 and outlet tube piece 12 arealigned with one another and with the above-mentioned measuring tubelongitudinal axis L as exactly as possible and are, advantageously,provided as one piece, so that e.g. a single, tubular stock can servefor their manufacture; in case required, measuring tube 10 and tubepieces 11, 12 can, however, also be manufactured by means of separate,subsequently joined, e.g. welded, stock. For manufacture of themeasuring tube 10, as well as the inlet and outlet, tubular pieces 11,12, practically every usual material for such measurement pickups can beused, such as e.g. alloys of iron, titanium, zirconium and/or tantalum,synthetic materials, or ceramics. For the case where the measurementpickup is to be releasably assembled with the pipeline, first and secondflanges 13, 14 are preferably formed on the inlet tube piece 11 and theoutlet tube piece 12, respectively; if required, the inlet and outlettube pieces can, however, also be connected directly to the pipeline,e.g. by means of welding or brazing. Additionally, as shownschematically in FIG. 1, the transducer housing 100 is provided, fixedto the inlet and outlet tube pieces 11, 12, for accommodating themeasuring tube 10; compare, in this connection, FIGS. 1 and 2.

At least for measuring the mass flow rate m, the measuring tube 10 isexcited in a first useful mode of oscillation developed as a lateraloscillation mode, in which it executes, at least in part, oscillations,especially bending oscillations, laterally to an imaginary measuringtube longitudinal axis L, especially such that it bends laterallyoutwards, essentially oscillating at a natural bending eigenfrequency,according to a natural, first form of eigenoscillation. For the casewhere the medium is flowing in the connected pipeline and, consequently,the mass flow rate m is different from zero, the measuring tube 10,oscillating in the first useful mode of oscillation, induces Coriolisforces in the medium as it flows through. These, in turn, interact withthe measuring tube 10 and result, in the manner known to those skilledin the art, in an additional, sensor-detectable deformation of themeasuring tube 10 essentially according to a natural, second form ofeigenoscillation coplanarly superimposed on the first form ofeigenoscillation. The instantaneous shape of the deformation of themeasuring tube 10 is, in such case, especially as regards itsamplitudes, also dependent on the instantaneous mass flow rate m. Asusual in the case of such measurement pickups, anti-symmetric forms ofbending oscillation of two, or four, antinodes can e.g. serve as thesecond form of eigenoscillation, the so-called Coriolis mode. Sincenatural eigenfrequencies of such modes of lateral oscillation ofmeasuring tubes are known to depend, in special measure, also on thedensity ρ of the medium, also the density ρ can be measured, withoutmore, by means of the inline measuring device, in addition to the massflow rate m. In addition to the lateral oscillations, the at least onemeasuring 10 is also driven, at least at times, in a torsional mode ofoscillation, for producing viscosity-dependent, shear forces in theflowing medium. In this torsional mode of oscillation, the measuringtube is excited to torsional oscillations about an axis of torsionaloscillation extending essentially parallel to, or coinciding with, thelongitudinal axis L of the measuring tube. Essentially, this excitementis such that the measuring tube 10 is twisted about its longitudinalaxis L in a form of natural, torsional oscillation; compare, in thisconnection, e.g. also U.S. Pat. No. 4,524,610, U.S. Pat. No. 5,253,533,U.S. Pat. No. 6,006,609 or EP-A 1 158 289. The exciting of the torsionaloscillations can, in such case, occur either in alternation with thefirst useful mode of oscillation and separated therefrom, in a seconduseful mode of oscillation, or, at least in the case of mutuallydistinguishable oscillation frequencies, also simultaneously with thelateral oscillations in the first useful mode of oscillation. Stateddifferently, the measurement pickup works, at least at times, in adual-mode of operation, in which the at least one measuring tube 10 iscaused to vibrate alternatingly in at least two oscillation modesessentially independent of one another, namely in the lateraloscillation mode and in the torsional oscillation mode.

According to one embodiment of the invention, for producing the massflow rate-dependent Coriolis forces in the flowing medium, the measuringtube 10 is excited, at least at times, with a lateral oscillationfrequency, which corresponds as exactly as possible to a lowest naturalbending eigenfrequency of the measuring tube 10, so that, thus, thelaterally oscillating measuring tube 10, without fluid flowing throughit, is essentially symmetrically bowed outwards with respect to a middleaxis perpendicular to the longitudinal axis L of the measuring tube and,in doing so, exhibits a single oscillation antinode. This lowest bendingeigenfrequency can be, for example, in the case of a stainless steeltube serving as the measuring tube 10, of nominal diameter 20 mm, wallthickness about 1.2 mm and length about 350 mm, with the usualappendages, about 850 Hz to 900 Hz.

In a further embodiment of the invention, the measuring tube 10 isexcited, especially simultaneously to the lateral oscillations in theuseful mode, with a torsional oscillation frequency f_(excT), whichcorresponds as exactly as possible to a natural torsional eigenfrequencyof the measuring tube. A lowest torsional eigenfrequency can, forexample, lie in the case of a straight measuring tube about in the rangeof twice the lowest bending eigenfrequency.

As already mentioned, the oscillations of the measuring tube 11 aredamped, on the one hand, by transfer of oscillation energy, especiallyto the medium. On the other hand, however, oscillation energy can alsobe withdrawn from the vibrating measuring tube to a considerable degreeby the excitation of components mechanically coupled therewith intooscillations, components such as e.g. the transducer housing 100 or theconnected pipeline. For the purpose of suppressing or preventing apossible loss of oscillation energy to the environment, acounteroscillator 20 is, therefore, provided in the measurement pickupfixed to the inlet and outlet ends of the measuring tube 10. Thecounteroscillator 20 is, as shown schematically in FIG. 2, preferablyembodied as one piece. If required, the counteroscillator 20 can becomposed of multiple parts, as shown e.g. also in U.S. Pat. No.5,969,265, EP-A 317 340 or WO-A 00/14485, or it can be implemented bymeans of two separate counteroscillator portions fixed to the inlet andoutlet ends of the measuring tube 10; compare FIG. 6. Thecounteroscillator 20 serves, among other things, to balance themeasurement pickup dynamically for at least one, predetermined densityvalue of the medium, for example a density value most frequently to beexpected, or also a critical density value, to such an extent thattransverse forces and/or bending moments possibly produced in thevibrating measuring tube 10 are largely compensated; compare, in thisconnection, also U.S. Pat. No. 6,691,583. Moreover, thecounteroscillator 20 serves for the above-described case, where themeasuring tube 10 is also excited during operation to torsionaloscillations, additionally to produce counter torsional moments largelycompensating such torsional moments as are produced by the singlemeasuring tube 10 preferably twisting about its longitudinal axis L,thus holding the environment of the measurement pickup, especially,however, the connected pipeline, largely free of dynamic torsionalmoments. The counteroscillator 20 can, as shown schematically in FIGS. 2and 3, be embodied in tube shape and can be connected, for example, tothe inlet end 11# and the outlet end 12# of the measuring tube 10 insuch a manner that it is, as shown in FIG. 3, arranged essentiallycoaxially with the measuring tube 10. The counteroscillator 20 can bemade of practically any of the materials also used for the measuringtube 10, thus, for example, stainless steel, titanium alloys, etc.

The counteroscillator 20, which is, especially in comparison to themeasuring tube 10, somewhat less torsionally and/or bendingly elastic,is likewise caused to oscillate during operation and, indeed, withessentially the same frequency as the measuring tube 10, but out ofphase therewith, especially with opposite phase. To this end, thecounteroscillator 20 is caused to oscillate with at least one of itstorsional eigenfrequencies tuned as accurately as possible to thosetorsional oscillation frequencies, with which the measuring tube ispredominantly caused to oscillate during operation. Moreover, thecounteroscillator 20 is adjusted also in at least one of its bendingeigenfrequencies to at least one bending oscillation frequency withwhich the measuring tube 10, especially in the useful mode, is caused tooscillate, and the counteroscillator 20 is excited during operation ofthe measurement pickup also to lateral oscillations, especially bendingoscillations, which are developed essentially coplanarly with lateraloscillations of the measuring tube 10, especially the bendingoscillations of the useful mode.

In an embodiment of the invention shown schematically in FIG. 3, thecounteroscillator 20 has, for this purpose, grooves 201, 202, which makepossible an exact adjustment of its torsional eigenfrequencies,especially a sinking of the torsional eigenfrequencies through a sinkingof a torsional stiffness of the counteroscillator 20. Although thegrooves 201, 202 are shown in FIG. 2 or FIG. 3 essentially uniformlydistributed in the direction of the longitudinal axis L, they can, ifrequired, also be arranged, without more, distributed non-uniformly inthe direction of the longitudinal axis L. Moreover, the massdistribution of the counteroscillator can, as likewise shownschematically in FIG. 3, also be corrected by means of correspondingmass balancing bodies 101, 102 fixed to the measuring tube 10. Thesemass balancing bodies 101, 102 can be e.g. metal rings pushed onto themeasuring tube 10, or small metal plates fixed thereto.

For producing mechanical oscillations of the measuring tube 10, themeasurement pickup additionally includes an exciter arrangement 40,especially an electrodynamic one, coupled to the measuring tube. Theexciter arrangement 40 serves for converting an electrical exciter powerP_(exc) fed from the measuring device electronics, e.g. having aregulated exciter current i_(exc) and/or a regulated voltage, into ane.g. pulse-shaped, or harmonic, exciter moment M_(exc) and/or an exciterforce F_(exc) acting on, and elastically deforming, the measuring tube10. For achieving a highest possible efficiency and a highest possiblesignal/noise ratio, the exciter power P_(exc) is tuned as exactly aspossible such that predominantly the oscillations of the measuring tube10 in the useful mode are maintained, and, indeed, as accurately aspossible to an instantaneous eigenfrequency of the measuring tubecontaining the medium flowing therethrough. The exciter force F_(exc),as well as also the exciter moment M_(exc), can, in this case, as isshown schematically in FIG. 4 or FIG. 6, each be developedbidirectionally or, however, also unidirectionally, and can be adjustedin the manner known to those skilled in the art, e.g. by means of acurrent and/or voltage regulating circuit as regards their amplitude ande.g. by means of a phase locked loop as regards their frequency. Theexciter arrangement 40 can include, as usual in the case of suchvibratory measurement-pickups, for instance a plunger coil arrangementhaving a cylindrical exciter coil attached to the counteroscillator 20or to the inside of the transducer housing 100. In operation, theexciter coil has a corresponding exciter current i_(exc) flowing throughit. Additionally included in the exciter arrangement 40 is a permanentlymagnetic armature extending at least partially into the exciter coil andfixed to the measuring tube 10. Furthermore, the exciter arrangement 40can also be realized by means of a plurality of plunger coils, or alsoby means of electromagnets, such as e.g. shown in U.S. Pat. No.4,524,610 or WO-A 03/095950.

For detecting the oscillations of the measuring tube 10, the measurementpickup additionally includes a sensor arrangement 50, which produces, asa representation of vibrations of the measuring tube 10, a first,especially analog, oscillation measurement signal s₁ by means of a firstoscillation sensor 51 reacting to such vibrations. The oscillationsensor 51 can be formed by means of a permanently magnetic armature,which is fixed to the measuring tube 10 and interacts with a sensor coilmounted on the counteroscillator 20 or the transducer housing. To serveas the oscillation sensor 51, especially such sensors are suited, whichdetect a velocity of the deflections of the measuring tube 10, based onthe electrodynamic principle. However, also acceleration measuring,electrodynamic or even travel-distance measuring, resistive or opticalsensors can be used. Of course, other sensors known to those skilled inthe art as suitable for detection of such vibrations can be used. Thesensor arrangement 60 includes, additionally, a second oscillationsensor 52, especially one identical to the first oscillation sensor 51.The second sensor 52 provides a second oscillation measurement signal s₂likewise representing vibrations of the measuring tube 10. The twooscillation sensors 51, 52 are in this embodiment so arranged in themeasurement pickup 10, separated from one another along the length ofthe measuring tube 10, especially at equal distances from the halfwaypoint of the measuring tube 10, that the sensor arrangement 50 locallyregisters both inlet-end and outlet-end vibrations of the measuring tube10 and converts them into the corresponding oscillation measurementsignals s₁, s₂. The two oscillation measurement signals s₁, s₂, whichusually each exhibit a signal frequency corresponding to aninstantaneous oscillation frequency of the measuring tube 10, are, asshown in FIG. 2, fed to the measuring device electronics 50, where theyare preprocessed, especially digitized, and then suitably evaluated bymeans of corresponding components.

According to an embodiment of the invention, the exciter arrangement 40is, as, in fact, shown in FIGS. 2 and 3, so constructed and arranged inthe measurement pickup, that it acts, during operation, simultaneously,especially differentially, on the measuring tube 10 and on thecounteroscillator 20. In the case of this further development of theinvention, the exciter arrangement 40 is, as, in fact, shown in FIG. 2,advantageously so constructed and so arranged in the measurement pickup,that it acts, during operation, simultaneously, especiallydifferentially, on the measuring tube 10 and on the counteroscillator20. In the example of an embodiment shown in FIG. 4, the exciterarrangement 40 has, for such purpose, at least one first exciter coil 41a, through which the exciter current, or an exciter current component,flows at least at times during operation. The exciter coil 41 a is fixedto a lever 41 c connected to the measuring tube 10 and actsdifferentially on the measuring tube 10 and the counteroscillator 20 viathis lever and an armature 41 b fixed externally to thecounteroscillator 20. This arrangement has, among others, the advantagethat, on the one hand, the counteroscillator 20, and thus also thetransducer housing 20, is kept small in cross section and, in spite ofthis, the exciter coil 41 a is easily accessible, especially also duringassembly. Moreover, a further advantage of this embodiment of theexciter arrangement 40 is that possible used coil cups 41 d, whichespecially at nominal diameters of over 80 mm, have weights which can nolonger be ignored, are fixable on the counteroscillator 20 and,consequently, have practically no influence on the eigenfrequencies ofthe measuring tube 10. It is to be noted here, however, that, in caserequired, the exciter coil 41 a can also be held by thecounteroscillator 20 and the armature 41 b, then, by the measuring tube10.

In corresponding manner, the oscillation sensors 51, 52 can be sodesigned and arranged in the measurement pickup that the vibrations ofthe measuring tube 10 and the counteroscillator 20 are registereddifferentially by them. In the example of an embodiment shown in FIG. 5,the sensor arrangement 50 includes a sensor coil 51 a fixed to themeasuring tube 10, here outside of all principal axes of inertia of thesensor arrangement 50. The sensor coil 51 a is arranged as close aspossible to an armature 51 b fixed to the counteroscillator 20 andmagnetically so coupled with such, that a changing measurement voltageis induced in the sensor coil, influenced by rotary and/or lateral,relative movements between measuring tube 10 and counteroscillator 20 inchanging their relative position and/or their relative separation. Onthe basis of such an arrangement of the sensor coil 51 a, both theabove-mentioned torsional oscillations and the excited bendingoscillations can, advantageously, be registered simultaneously. Ifnecessary, the sensor coil 51 a therefor can, however, also be fixed tothe counteroscillator 20 and the armature 51 b coupled therewith can,correspondingly, then be fixed to the measuring tube 10.

In another embodiment of the invention, measuring tube 10,counteroscillator 20 and the sensor and exciter arrangements 40, 50secured thereto are so matched to one another with respect to their massdistribution, that the resulting inner part of the measurement pickup,suspended by means of the inlet and outlet tube pieces 11, 12, has acenter of mass MS lying at least inside of the measuring tube 10, andpreferably as close as possible to the longitudinal axis L of themeasuring tube. Additionally, the inner part is advantageously soconstructed that it has a first principal axis of inertia T₁ alignedwith the inlet tube piece 11 and the outlet tube piece 12 and lying atleast sectionally within the measuring tube 10. Due to the displacementof the center of mass MS of the inner part, especially, however, alsodue to the above-described position of the first principal axis ofinertia T₁, the two oscillation forms assumed in operation by themeasuring tube 10 and largely compensated by the counteroscillator 20,namely the torsional oscillations and the bending oscillations of themeasuring tube 10, are highly mechanically decoupled from one another;compare, in this connection, also WO-A 03/095950. In this way, the twoforms of oscillation, thus lateral oscillations and/or torsionaloscillations, are advantageously, without more, excited separately fromone another. Both the displacement of the center of mass MS and also thefirst principal axis of inertia T₁ toward the longitudinal axis of themeasuring tube can, for example, be considerably simplified by havingthe inner part, thus measuring tube 10, counteroscillator 20 and thesensor and exciter arrangements 50, 40 secured thereto, so constructedand arranged with respect to one another, that a mass distribution ofthe inner part along the length of the measuring tube longitudinal axisL is essentially symmetrical, at least, however, invariant relative toan imaginary rotation about the longitudinal axis L of the measuringtube by 180° (c2-symmetry). Additionally, the counteroscillator 20—heretubularly, especially also largely axially symmetrically, embodied—isarranged essentially coaxially with the measuring tube 10, whereby thereaching of a symmetrical distribution of mass in the inner part issignificantly simplified, and, consequently, also the center of mass MSis displaced in simple manner close to the longitudinal axis L of themeasuring tube.

Moreover, the sensor and exciter arrangements 50, 40 in the example ofan embodiment presented here are so constructed and arranged relative toone another on the measuring tube 10 and, where appropriate, on thecounteroscillator 20, that a mass moment of inertia produced by them isdeveloped as concentrically as possible to the longitudinal axis L ofthe measuring tube or at least is kept as small as possible. This cane.g. be achieved by having a common center of mass of sensor and exciterarrangements 50, 40 lie as close as possible to the longitudinal axis Lof the measuring tube and/or by keeping the total mass of sensor andexciter arrangements 50, 40 as small as possible.

In a further embodiment of the invention, the exciter arrangement 40 is,for the purpose of the separated exciting of torsional and/or bendingoscillations of the measuring tube 10, so constructed and so fixed tothe measuring tube 10 and to the counteroscillator 20, that a forceproducing the bending oscillations acts on the measuring tube 10 in thedirection of an imaginary line of force extending outside of a secondprincipal axis of inertia T₂ perpendicular to the first principal axisof inertia T₁, or intersecting the second principal axis of inertia in,at most, one point. Preferably, the inner part is so embodied that thesecond principal axis of inertia T₂ is essentially the above-mentionedmiddle axis. In the example of an embodiment shown in FIG. 4, theexciter arrangement 40 has, for this purpose, at least one first excitercoil 41 a, through which the exciter current or an exciter currentcomponent flows at least at times during operation. Exciter coil 41 a isfixed to a lever 41 c connected with the measuring tube 10 and via thislever and an armature 41 b fixed externally to the counteroscillator 20,acts differentially on the measuring tube 10 and the counteroscillator20. This arrangement has, among other things, also the advantage that,on the one hand, the counteroscillator 20 and, consequently, also thetransducer housing 100 are kept small in cross section and, in spite ofthis, the exciter coil 41 a is easily accessible, especially also duringassembly. Moreover, a further advantage of this embodiment of theexciter arrangement 40 is that possibly used coil cups 41 d, whichespecially at nominal diameters of over 80 mm have weights that nolonger can be neglected, can likewise be fixed to the counteroscillator20 and, consequently, have practically no effect on the resonancefrequencies of the measuring tube. It should be noted here that, whenrequired, the exciter coil 41 a can also be mounted to thecounteroscillator 20 and then the armature 41 b is held by the measuringtube 10.

According to a further embodiment of the invention, the exciterarrangement 40 has at least one, second exciter coil 42 a arranged alonga diameter of the measuring tube 10 and coupled with the measuring tube10 and the counteroscillator 20 in the same way as the exciter coil 41a. According to another, preferred embodiment of the invention, theexciter arrangement has two further exciter coils 43 a, 44 a, thus atotal of four, at least arranged symmetrically with respect to thesecond principal axis of inertia T₂. All coils are mounted in themeasurement pickup in the above-described manner. The force acting onthe measuring tube 10 outside of the second principal axis of inertia T₂can be produced by means of such two, or four, coil arrangements insimple manner e.g. by having one of the exciter coils, e.g. the excitercoil 41 a, exhibit another inductance than the respective others, or bycausing to flow through one of the exciter coils, e.g. the exciter coil41 a, during operation, an exciter current component that is differentfrom a respective exciter current component of the respectively otherexciter coils.

According to another embodiment of the invention, the sensor arrangement50 includes, as shown schematically in FIG. 5, a sensor coil 51 aarranged outside of the second principal axis of inertia T₂ and fixed tomeasuring tube 10. The sensor coil 51 a is arranged as near as possibleto an armature 51 b fixed to the counteroscillator 20 and ismagnetically coupled therewith such that a changing measurement voltageis induced in the sensor coil, influenced by rotary and/or lateralrelative movements between measuring tube 10 and counteroscillator 20 asthey change their relative positions and/or their relative separations.Due to the arrangement of the sensor coil 51 a according to theinvention, both the above-described torsional oscillations and thebending oscillations, excited where appropriate, can be registered inadvantageous manner simultaneously. If required, the sensor coil 51 atherefor can, instead, be fixed to the counteroscillator 20 and, incorresponding manner, the armature 51 b coupled therewith can be fixedto the measuring tube 10.

It is noted here, additionally, that the exciter arrangement 40 and thesensor arrangement 50 can also have, in the manner known to thoseskilled in the art, essentially the same mechanical structure;consequently, the above-described embodiments of the mechanicalstructure of the exciter arrangement 40 can essentially also betransferred to the mechanical structure of the sensor arrangement 50,and vice versa.

For vibrating the measuring tube 10, the exciter arrangement 40 is, asalready mentioned, fed with a likewise oscillating exciter currenti_(exc), especially a multifrequency current, of adjustable amplitudeand adjustable exciter frequency f_(exc) such that this current flowsthrough the exciter coils 26, 36 during operation and the magneticfields required for moving the armatures 27, 37 are produced incorresponding manner. The exciter current i_(exc) can be e.g.harmonically multifrequent or even rectangular. The lateral oscillationexciter frequency f_(excL) of a lateral current component i_(excL) ofthe exciter current i_(exc) required for maintaining the lateraloscillations of the measuring tube 10 can advantageously be so chosenand adjusted in the case of the measurement pickup shown in the exampleof an embodiment that the laterally oscillating measuring tube 10oscillates essentially in a bending oscillation base mode having asingle oscillation antinode. Analogously thereto, also a torsionaloscillation frequency f_(excT) of a torsional current component i_(excT)of the exciter current i_(exc) required for maintaining the torsionaloscillations of the measuring tube 10 can advantageously be so chosenand adjusted in the case of the measurement pickup shown in the exampleof an embodiment that the torsionally oscillating measuring tube 10oscillates essentially in a torsional oscillation base mode having asingle oscillation antinode. The two mentioned current componentsi_(excL) and i_(excT) can, depending on the type of operation selected,be fed into the exciter arrangement 40 intermittently, thusinstantaneously each acting as the exciter current i_(exc), or alsosimultaneously, thus supplementing one another to form the effectiveexciter current i_(exc).

For the above-described case wherein the lateral oscillation frequencyf_(excL) and the torsional oscillation frequency f_(excT), with whichthe measuring the measuring tube 10 is caused to oscillate duringoperation, are adjusted differently from one another, a separation ofthe individual oscillation modes can occur both in the exciter signalsand also in the sensor signals, by means of the measurement pickup insimple and advantageous manner, even in the case of simultaneouslyexcited torsional and bending oscillations, e.g. based on a signalfiltering or a frequency analysis. Otherwise, an alternating exciting ofthe lateral and torsional oscillations recommends itself.

For producing and adjusting the exciter current i_(exc), or the currentcomponents i_(excL), i_(excT), the measuring device electronics includesa corresponding driver circuit 53, which is controlled by a lateraloscillation frequency adjustment signal y_(FML) representing the desiredlateral oscillation exciter frequency f_(excL) and by a lateraloscillation amplitude adjustment signal y_(AML) representing the desiredlateral oscillation amplitude of the exciter current i_(exc) and/or thelateral current component i_(excL), as well as, at least at times, by atorsional oscillation frequency adjustment signal y_(FMT) representingthe torsional oscillation exciter frequency f_(excT) and by a torsionaloscillation amplitude adjustment signal y_(FMT) representing the desiredtorsional oscillation amplitude of the exciter current i_(exc) and/orthe torsional current component i_(excT). The driver circuit 53 can berealized e.g. by means of a voltage-controlled oscillator or adownstream voltage-to-current converter; instead of an analogoscillator, however, also a numerically controlled, digital oscillatorcan be used to set the instantaneous exciter current i_(exc) or thecomponents i_(excL), i_(excT) of the exciter current.

An amplitude control circuit 51 integrated into the measuring deviceelectronics 50 can serve for producing the lateral amplitude adjustmentsignal y_(AML) and/or the torsional oscillation amplitude adjustmentsignal y_(AML). The amplitude control circuit 51 actualizes theamplitude adjustment signals y_(AML), y_(AMT) on the basis ofinstantaneous amplitudes of at least one of the two oscillationmeasurement signals s₁, s₂ measured at the instantaneous lateraloscillation frequency and/or the instantaneous torsional oscillationfrequency, as well as on the basis of corresponding, constant orvariable amplitude reference values for the lateral and torsionaloscillations, respectively W_(B), W_(T); as appropriate, alsoinstantaneous amplitudes of the exciter current i_(exc) can bereferenced for generating the lateral oscillation amplitude adjustmentsignal y_(AML) and/or the torsional oscillation amplitude adjustmentsignal y_(AMT); compare FIG. 7. Construction and manner of operation ofsuch amplitude control circuits are likewise known to those skilled inthe art. As an example for such an amplitude control circuit, referenceis made, moreover, to the measurement transmitters of the series“PROMASS 80”, such as are available from the assignee, for example inconnection with measurement pickups of the series “PROMASS I”. Theiramplitude control circuit is preferably so constructed that the lateraloscillations of the measuring tube 10 are controlled to a constantamplitude, thus an amplitude also independent of the density ρ.

The frequency control circuit 52 and the driver circuit 53 can beconstructed e.g. as phase-locked loops, which are used in the mannerknown to those skilled in the art for adjusting the lateral oscillationfrequency adjusting signal y_(FML) and/or the torsional oscillationfrequency adjusting signal y_(FMT) continuously for the instantaneouseigenfrequencies of the measuring tube 10 on the basis of a phasedifference measured between at least one of the oscillation measurementsignals s₁, s₂ and the exciter current i_(exc) to be adjusted,respectively the instantaneously measured exciter current i_(exc). Theconstruction and use of such phase-locked loops for the driving ofmeasuring tubes at one of their mechanical eigenfrequencies is describedin detail in e.g. U.S. Pat. No. 4,801,897. Of course, other frequencycontrol circuits known to those skilled in the art can be used, such asare proposed in U.S. Pat. No. 4,524,610 or U.S. Pat. No. 4,801,897.Furthermore, reference is made to the already mentioned measurementtransmitters of the series “PROMASS 80” respecting a use of suchfrequency control circuits for vibratory measurement pickups. Othercircuits suitable for use as driver circuits can be learned from, forexample, U.S. Pat. No. 5,869,770 or U.S. Pat. No. 6,505,519.

According to a further embodiment of the invention, the amplitudecontrol circuit 51 and the frequency control circuit 52 are, as shownschematically in FIG. 7, realized by means of a digital signal processorDSP provided in the measuring device electronics 50 and by means ofprogram code correspondingly implemented in such and running therein.The program codes can be stored persistently or even permanently e.g. ina non-volatile memory EEPROM of a microcomputer 55 controlling and/ormonitoring the signal processor and loaded upon startup of the signalprocessor DSP into a volatile data memory RAM of the measuring deviceelectronics 50, e.g. RAM integrated in the signal processor DSP. Signalprocessors suited for such applications are e.g. those of typeTMS320VC33 available from the firm Texas Instruments Inc. It is clear,in this regard, that the oscillation measurement signals s₁, s₂ need tobe converted by means of corresponding analog-to-digital converters A/Dinto corresponding digital signals for a processing in the signalprocessor DSP; compare, in this connection, especially EP-A 866,319. Incase required, adjustment signals output from the signal processor, suchas e.g. the amplitude adjusting signals y_(AML), y_(AMT), or thefrequency adjusting signals yL, YFMT, can be, in corresponding manner,converted from digital to analog.

As shown in FIG. 7, the, if appropriate, first suitably conditioned,oscillation measurement signals s₁, s₂ are additionally sent to ameasurement circuit 21 of the measuring device electronics for producingthe at least one measured value X_(X) on the basis of at least one ofthe oscillation measurement signals s₁, s₂ and/or on the basis of theexciter current i_(exc).

According to an embodiment of the invention, the measurement circuit 21is constructed, at least in part, as a flow rate calculator and themeasurement circuit serves for determining, in the manner known per seto those skilled in the art, from a phase difference detected betweenthe oscillation measurement signals s₁, s₂ generated in the case of ameasuring tube 10 oscillating laterally at least in part, a measuredvalue X_(X) serving here as a mass flow rate measured value andrepresenting, as accurately as possible, the mass flow rate to bemeasured. The measurement circuit 21 can be any, especially digital,measuring circuit already used in conventional Coriolis mass flowmeasuring devices for determining the mass flow rate on the basis of theoscillation measurement signals s₁, s₂; compare, in this connection,especially the initially mentioned WO-A 02/37063, WO-A 99/39164, U.S.Pat. No. 5,648,616, U.S. Pat. No. 5,069,074. Of course, other measuringcircuits known to those skilled in the art to be suitable for Coriolismass flow measuring devices can be used, i.e. measuring circuits whichmeasure, and correspondingly evaluate, phase and/or time differencesbetween oscillation measurement signals of the described kind.

Additionally, the measurement circuit 21 can also serve to utilize anoscillation frequency of the at least one measuring tube 11, asmeasured, for example, on the basis of at least one of the oscillationmeasurement signals s₁, s₂, for generating a measured value X_(x) usableas a density measured value instantaneously representing a density ρ tobe measured for the medium or a phase of the medium.

Because the straight measuring tube 10 is, as above described, caused toexecute, during operation, lateral and torsional oscillationssimultaneously or alternatingly, the measurement circuit can also beused to determine (derived from the exciter current i_(exc), which, itis known, can serve also as a measure for an apparent viscosity or alsoa viscosity-density product) a measured value X_(x) usable as aviscosity measured value and instantaneously representing a viscosity ofthe medium; compare, in this connection, also U.S. Pat. No. 4,524,610 orWO-A 95 16 897.

It is clear in this connection, without more, for those skilled in theart, that the inline measuring device can determine the separatemeasured values X_(x) for the various measured quantities x both in acommon measuring cycle, thus with equal updating rates, as well as withdifferent updating rates. For example, a very accurate measurement ofthe usually significantly varying mass flow rate requires usually a veryhigh updating rate, while the comparatively less variable viscosity ofthe medium can, where appropriate, be updated at larger separations intime. Additionally, it can, without more, be assumed that currentlydetermined, measured values X_(x) can be stored temporarily in themeasuring device electronics and, therefore, be available for subsequentuses. Advantageously, the measurement circuit 21 can, furthermore, alsobe implemented by means of the signal processor DSP.

As already mentioned at the start, inhomogeneities and/or the formationof first and second phases in the flowing medium, for example gasbubbles and/or solid particles entrained in liquids, can lead to theresult that a measured value determined in conventional manner assuminga single-phase and/or homogeneous medium will not match with sufficientaccuracy the actual value of the quantity x whose measurement isdesired, for example the mass flow rate m, i.e. the measured value mustbe appropriately corrected. This preliminarily determined, provisionallyrepresenting, or at least corresponding, value of the physical quantityx whose measurement is desired, which value, as already explained, can,for example, be a phase difference Δφ measured between the oscillationmeasurement signals s₁, s₂, or a measured oscillation frequency, of themeasuring tube 11, is, consequently, referenced in the following as aninitial measured value, or also a beginning measured value, X′_(x). Fromthis initial measured value X′_(x), the evaluation electronics 21, inturn, finally derives the measured value X_(x) representing thephysical, measured quantity x sufficiently accurately, whether thephysical, measured quantity x is the mass flow rate, the density, or theviscosity. Considering the very comprehensive and very well documentedand detailed state of the art, it can be assumed that the determinationof the initial measured value X′_(x), which, for practical purposes,corresponds to the measured value generated in conventional manner,presents no difficulties for those skilled in the art, so that theinitial measured value X′_(x) can be taken as a given for the furtherexplanation of the invention.

There is already discussion in the state of the art with reference tothe mentioned inhomogeneities in the medium that these can immediatelyshow up both in the phase difference measured between the twooscillation signals s₁, s₂ and in the oscillation amplitude or theoscillation frequency of each of the two oscillation measurementsignals, respectively exciter current, thus in practically all of theusually measured, directly or indirectly, operational parameters ofmeasuring devices of the described kind. This is true, especially in thecase of the operational parameters determined with a laterallyoscillating measuring tube, as is treated in WO-A 03/076880 or U.S. Pat.No. 6,505,519; it can, however, also not always be excluded foroperational parameters measured with a torsionally oscillating measuringtube—compare, in this connection, especially U.S. Pat. No. 4,524,610.

Further investigations by the inventors have, however, led to thesurprising discovery that, while it is true, the instantaneous excitercurrent i_(exc) and, going along therewith, a damping of theoscillations of the measuring tube 10 usually likewise measured in theoperation of the measuring device, do depend to a significant amount onthe degree of the inhomogeneity of the two, or more, phase medium and/oron a concentration of a second medium phase thereof, for example, thuson a characteristic, a distribution and/or an amount of gas bubblesand/or solid particles entrained in a liquid being measured,nevertheless, both for lateral and for torsional oscillations—at leastin the two base modes mentioned above a largely reproducible and,consequently, at least experimentally determinable relationship can bepostulated between the particular current component i_(excL), i_(excT)instantaneously required for maintaining the lateral, respectivelytorsional, oscillation and the instantaneous degree of inhomogeneity ofthe two, or more, phase medium, or even the instantaneous concentrationof a second phase of the medium, especially a second phase acting as adisturbance.

Surprisingly, it has additionally been found that, in spite of the factthat both an instantaneous damping of the lateral oscillations and, asis discussed especially in U.S. Pat. No. 4,524,610 or EP-A 1 291 639, aninstantaneous damping of the torsional oscillations are dependentsignificantly on the degree of the inhomogeneity or on theconcentrations of individual phases of the medium, simultaneous, or atleast contemporaneous, determination of the instantaneous dampings ofboth of the oscillation modes permits an amazingly robust and veryreproducible correction of the intermediate value X′_(x) and, therefore,the generating of a very accurate measured value X_(x). Furtherinvestigations have shown, namely, that the damping both of the lateraloscillations and the torsional oscillations is, indeed, very stronglydependent on the viscosity of the medium to be measured. At the sametime, the damping of the lateral oscillations shows a very strongdependence on the degree of inhomogeneities of the mediuminstantaneously present in the measuring tube 10, while, in contrast,the dependence of the damping of the torsional oscillations oninhomogeneities in the medium is far weaker.

According to the invention, for the purpose of improving the accuracywith which the physical, measured quantity x, for example the mass flowrate m or the density ρ, is determined, the measurement pickup isoperated, at least at times, in the previously mentioned dual-mode, inwhich the at least one measuring tube 10—in turns and/oralternatingly—is caused to vibrate in the lateral oscillation modeand/or in the torsional oscillation mode. For the correction of thefirst determined, initial, measured value X′_(x) sought accordingly, themeasuring device electronics 2 determines, during operation, an,especially digital, first intermediate value X₁, which essentiallycorresponds to the damping of the lateral oscillation mode, and an,especially digital, second intermediate value X₂, which essentiallycorresponds to the medium-dependent damping of the torsional oscillationmode. The determining of the first intermediate value proceeds hereessentially based on the lateral current component i_(excL) of theexciter current i_(exc), especially the regulated component, requiredfor maintaining the lateral oscillations, while, for determining thesecond intermediate value X₂, especially the torsional current componenti_(excT), especially the regulated component, required for maintainingthe torsional oscillations is taken into consideration.

Using the two intermediate values X₁, X₂, the measurement circuit 21additionally determines an, especially likewise digital, correctionvalue X_(K) for the intermediate value X′_(x). The correction of theintermediate value X′_(x) on the basis of the correction value X_(K), aswell as the generating of the measured value X_(x), can occur in themeasuring device electronics, for example, based on the mathematicalrelationshipX _(x) =K _(x)(1+X _(K))·X _(x)′.  (1)

In an embodiment of the invention, the correction value X_(K) isdetermined by means of the measuring device electronics based on themathematical relationshipX _(K) =K _(K)·(X ₁ −X ₂),  (2)so that this essentially represents a measure of the deviation AD ofdamping measured during operation for the principally excited, lateraland torsional oscillations. Alternatively, or for supplementing such,the correction value X_(K) can also be determined based on themathematical relationship $\begin{matrix}{X_{K} = {K_{K}^{\prime} \cdot {\left( {1 - \frac{X_{2}}{X_{1}}} \right).}}} & (3)\end{matrix}$

While, thus, in Eq. (2), the correction value X_(K) is determined on thebasis of a difference AD existing between the intermediate value X₁ andthe intermediate value X₂, in the case of Eq. (3), the correction valueX_(K) is determined on the basis of a comparison of the secondintermediate value X₂ with the first intermediate value X₁. In thisrespect, the correction value X_(K) represents, at least for a two-phasemedium, also a measure for an instantaneous, relative or absolute,concentration of a first and a second phase of a medium, especially forgas bubbles in a liquid. Besides the generating of the actual measuredvalue X_(x), the correction value X_(K) can, therefore, also beconverted into a concentration measured value X_(C), which represents,in the case of a two, or more, phase medium in a measuring tube, an,especially relative, volume and or mass fraction of a phase of a medium.Furthermore, the correction value X_(K) can also be used to signalizethe degree of inhomogeneity of the medium, or measured values derivedtherefrom, such as e.g. a percentage air content in the medium or avolume, quantity or mass fraction of solid particles entrained in themedium, e.g. on site or visually perceivable in a remote control room.Alternatively or additionally, the correction value X_(K) can also servefor signalizing for the user, for example out of a comparison with aninitially defined limit value, that, for the instantaneous flowconditions in the measuring tube 10, the measured quantity x is beingmeasured with considerable uncertainty and/or with a large amount oferror. Additionally, the correction value X_(K) can, in this case, alsobe used to switch off a signal output which issues the measured valueX_(x) for the measured quantity x of interest during operation.

Further experimental investigations have shown that, for a measurementpickup of the illustrated example of an embodiment, the consideration ofthe instantaneous lateral oscillation frequency of the vibratingmeasuring tube can lead to a further improvement of the accuracy of themeasured value X_(x). Moreover, by a normalizing of the correction valueX_(K) determined on the basis of Eq. (2) or Eq. (3) on the square rootof the instantaneous lateral oscillation frequency, one finds that thecorrection value X_(K) is essentially proportional to the gas fraction,at least for the case wherein a liquid, for example glycerin, containsentrained gas bubbles, for example air; compare, in this connection,also FIG. 9. Therefore, in a further development of the invention, Eq.(2) is modified using a lateral oscillation frequency measured valueX_(fexcL) representing the instantaneous lateral oscillation frequency,as follows: $\begin{matrix}{X_{K} = {K_{K} \cdot {\frac{\left( {X_{1} - X_{2}} \right)}{\sqrt{X_{fexcL}}}.}}} & (4)\end{matrix}$

The determining of the lateral oscillation frequency measured value cantranspire simply e.g. on the basis of the above-mentioned lateraloscillation frequency adjusting signal y_(FML).

In the determining of the two intermediate values X₁, X₂, it isadditionally to be kept in mind that the damping of the oscillations ofthe measuring tube 10 is determined both by the damping componentattributable to viscous frictions within the medium and by a dampingcomponent which is practically independent of the medium. This latterdamping component is caused by mechanical friction forces, which acte.g. in the exciter arrangement 40 and in the material of the measuringtube 10. Stated differently, the instantaneously measured excitercurrent i_(exc) represents the totality of the frictional forces and/orfrictional moments in the measurement pickup 10, including themechanical frictions in the measurement pickup and the viscous frictionin the medium. In determining the intermediate values X₁, X₂, which, asmentioned, mainly are related to the damping components of theoscillations of the measuring tube resulting from viscous frictions inthe medium, the mechanical damping components, which are independent ofthe medium, must be appropriately considered, for example they should beseparated out or eliminated.

For determining the intermediate value X₁, therefore, an embodiment ofthe invention provides that, from an, especially digital, lateralcurrent measured value X_(iexcL) instantaneously representing thelateral current component i_(excL), a correspondingly associated,lateral, empty-state, electrical current, measured value K_(iexcL) issubtracted, which represents the mechanical friction forces in each casearising in the instantaneously excited, lateral oscillation mode in themeasurement pickup in the case of empty measuring tube 10. In the samemanner, for determining the intermediate value X₂, from an, especiallydigital, torsional current measured value X_(iexcT) instantaneouslyrepresenting the torsional current component i_(excT), a torsional,empty-state, electrical current, measured value K_(iexcT) is subtracted,which represents the mechanical frictional forces in each case arisingin the instantaneously excited, torsional oscillation mode in themeasurement pickup in the case of empty measuring tube 10.

According to a further embodiment of the invention, the determining ofthe intermediate value X₁ occurs, as also shown in FIG. 8 by way ofexample on electrical current, measured values X_(iexcL), X_(iexcT) andempty-state, electrical current, measured values K_(iexcL), K_(iexcT)experimentally determined for the correction of the mass flow rate onthe basis of the lateral current component i_(excL) driving the lateraloscillations and on the basis of the associated lateral, empty-state,electrical current, measured value K_(iexcL), especially based on themathematical relationshipX ₁ =K ₁·(X _(iexcL) −K _(iexcL))  (5)and/or based on the mathematical relationship $\begin{matrix}{X_{1} = {K_{1}^{\prime} \cdot {\left( {1 - \frac{K_{iexcL}}{X_{iexcL}}} \right).}}} & (6)\end{matrix}$

In case required, especially in the case of significantly varying,vibratory measuring tube, oscillation amplitudes and/or vibratorymeasuring tube, oscillation amplitudes deviating from the calibratedreference values, the lateral current component i_(excL) can initiallylikewise be normalized on the instantaneous oscillation amplitude of thelateral oscillations of the measuring tube, for example using theoscillation measurement signals s₁, s₂.

Analogously thereto, also the intermediate value X₂ can be determinedbased on the mathematical relationshipX ₂ =K ₂·(X _(iexcT) −K _(iexcT))  (7)and/or based on the mathematical relationship $\begin{matrix}{X_{2} = {K_{2}^{\prime} \cdot {\left( {1 - \frac{K_{iexcT}}{X_{iexcT}}} \right).}}} & (8)\end{matrix}$

Each of the empty-state, electrical current, measured values K_(iexcL),K_(iexcT), as also the device-specific coefficients K_(k), K_(k)′, K₁,K₂, K₁ or K₂′ is likewise to be determined during a calibration of theinline measuring device, e.g. using an evacuated or air-carryingmeasuring tube, and stored, or set, appropriately in the measuringdevice electronics 50, especially normalized on the oscillationamplitude measured at such time. It is clear, without more, for thoseskilled in the art, that, if necessary, other physical parametersinfluencing the empty-state, electrical current, measured valuesK_(iexcL), K_(iexcT), such as e.g. an instantaneous temperature of themeasuring tube and/or of the medium, are to be taken into considerationduring the calibration. For calibrating the measured values pickup 10,usually two, or more, different, two, or more, phase, media withvarying, but known, flow parameters, such as e.g. known concentrationsof the individual medium phases of the calibrating medium, whose densityρ, mass flow rate m, viscosity η and/or temperature are known, arecaused to flow in turn through the measurement pickup 10, and thecorresponding reactions of the measured values pickup 10, such as e.g.the instantaneous exciter current i_(exc), the instantaneous lateraloscillation exciter frequency f_(excL) and/or the instantaneoustorsional oscillation exciter frequency f_(excT) are measured. Theadjusted flow parameters and the respectively measured reactions of themeasured operational parameters of the measurement pickup 10 are relatedto one another in appropriate manner and, thus, mapped onto thecorresponding calibration constants. For example, for determining theconstants during the calibration measurements for two calibration mediaof known viscosity held as constant as possible and of differentinhomogeneity, which, however, in each case, is formed in a manner whichremains constant, a ratio X_(x)′/x and/or X_(x)/x of the intermediatevalue X_(x)′ determined in each case, respectively, of the measuredvalue X_(x) determined in each case, to the then, in each case, current,actual value of the quantity being measured is formed for known airfraction. For example, the first calibration medium can be flowingwater, or even oil, with entrained air bubbles, and the secondcalibration medium can be water which is as homogeneous as possible. Thecalibration constants determined here can then be stored e.g. in theform of digital data in a table memory of the measuring deviceelectronics; they can, however, also serve as analog adjustment valuesfor corresponding computing circuits. It is to be noted here that thecalibration of measurement pickups of the described type is a subjectknown per se, or at least executable from the above explanations, forthose skilled in the art, and, consequently does not require any furtherexplanation. Advantageously, the already mentioned lateral oscillationamplitude adjustment signal y_(AML) and/or the torsional oscillationamplitude adjustment signal y_(AMT) can be used for determining thelateral current, measured value X_(iexcL) and/or the torsional current,measured value X_(iexcT), since these represent the exciter currenti_(exc), or its components i_(excL), i_(excT) sufficiently accuratelyfor the correction.

According to a further embodiment of the invention, for the alreadymultiply-mentioned case where the measured quantity x to be registeredcorresponds to a viscosity, or even a fluidity, and so the measuredvalue X_(x) serves as a viscosity measured-value, also the initialmeasured-value X_(x)′ is determined on the basis of the exciter currenti_(exc) driving the exciter arrangement 40 in the case of a measuringtube at least partially torsionally oscillating, especially on the basisof the torsional current component i_(excT) serving for maintaining thetorsional oscillations of the measuring tube 10. Taking intoconsideration the relationship already described in U.S. Pat. No.4,524,610:√{square root over (η)}˜i_(excT),  (9)according to which the torsional current component i_(excT), reduced bythe above-mentioned, torsional, empty-state, electrical current,measured value K_(iexcT), correlates very well with the square root ofthe actual viscosity, η, at least in the case of constant density, ρ,and largely homogeneous medium, in corresponding manner first a squaredvalue X_(ΔiexcT) ² of the torsional current, measured value X_(iexcT) isformed inside the measuring device electronics, reduced by thetorsional, empty-state, electrical current, measured value K_(iexcT) andderived from the exciter current i_(exc), for the determining of theinitial measured value X_(x)′. Considering that, as, in fact, alsoexplained in U.S. Pat. No. 4,524,610, the square of the current does, infact, provide the information on the product of density and viscosity,the actual density, which, for example, can be determined initially,likewise by means of the inline measuring device, is, moreover, to betaken into consideration when determining the initial measured valueX_(x)′ in the aforedescribed manner.

In a further embodiment of the invention, for forming the initialmeasured value X_(η), the square X_(iexcT) ² of the torsional current,measured value X_(iexcT) is, moreover, by means of a simple, numericaldivision, normalized on an amplitude measured value X_(sT), whichrepresents instantaneously, in the case of a torsionally oscillatingmeasuring tube, an operationally determined, in certain cases varying,signal amplitude of at least one of the oscillation measurement signalss₁, s₂. It has, namely, also been found, that, for such viscositymeasuring devices having such a vibratory measurement pickup, especiallyalso in the case of constantly controlled oscillation amplitude and/orin the case of simultaneous exciting of lateral and torsionaloscillations, a ratio i_(exc)/θ of the exciter current i_(exc) to apractically not directly measurable velocity θ of a movement causing theinternal frictions and, thus, also the frictional forces in the medium,is a more accurate estimate of the already mentioned damping actingagainst the excursions of the measuring tube 10. Consequently, forfurther increasing the accuracy of the measured value X_(x), especially,however, also for decreasing its sensitivity to fluctuating oscillationamplitudes of the vibrating measuring tube 10 possibly arising duringoperation, it is further provided that, for the determining of theinitial measured value X_(x)′, the torsional current measured valueX_(iexcT) is first normalized on the amplitude measured value X_(sT),which represents the above-mentioned velocity θ sufficiently accurately.Stated differently, a normalized torsional current measured valueX′_(iexcT) is formed according to the following formula: $\begin{matrix}{X_{iexcT}^{\prime} = {\frac{X_{iexcT}}{X_{sT}}.}} & (10)\end{matrix}$

The amplitude measured value X_(s1) is, based on the recognition thatthe movement causing the viscous friction in the medium matches verystrongly the movement of the vibrating measuring tube 10 registeredlocally by means of the sensor 51 or also by means of the sensor 52,preferably derived using the measuring device electronics 50, e.g. bythe internal amplitude measurement circuit, from at least one, possiblyalready digitized, sensor signal s₁. It is noted here, again, that thesensor signal s₁ is preferably proportional to a velocity of an,especially lateral, excursion of the vibrating measuring tube 10; thesensor signal s₁ can, however, also be proportional to an accelerationacting on the vibrating measuring tube or to a distance covered by thevibrating measuring tube 10. For the case, where the sensor signal s₁ isdesigned to be velocity-proportional in the above sense, this is, ofcourse, to be considered in the determining of the initial measuredvalue.

The aforementioned functions serving for the production of the measuredvalue X_(x), symbolized by the Eqs. (1) to (10), can be implemented, atleast in part, by means of the signal processor DSP or e.g. also bymeans of the above-mentioned microcomputer 55. The creation andimplementation of corresponding algorithms matching such equations ormimicking the functioning of the amplitude control circuit 51,respectively the frequency control circuit 52, and their transformationinto program code executable in such signal processors, is, per se,within the skill of the art, and, consequently, does not require anydetailed explanation, particularly once the present disclosure has beenreviewed. Of course, these equations can also, without more, berepresented by means of corresponding, discretely assembled, analogand/or digital, simulating circuits in the measuring device electronics50.

In a further development of the invention, the correction value X_(K)instantaneously appropriate during operation is determined, startingfrom the intermediate values X₁, X₂, practically directly byrepresenting in the measuring device electronics, especially in aprogram, a unique relationship between a present combination of the twointermediate values X₁, X₂ and the correction value X_(K) belongingtherewith. To this end, the measuring device electronics 2 additionallyhas a table memory, in which a set of predetermined, digital correctionvalues X_(K,i) is stored, for example values determined during thecalibration of the Coriolis mass flow measuring device. These correctionvalues X_(K,i) are accessed directly by the measurement circuit via amemory address determined by means of the instantaneously validintermediate values X₁, X₂. The correction value X_(K) can be determinede.g. in simple manner by comparing a combination of the instantaneouslydetermined intermediate values X₁, X₂, for example the above-mentioneddamping difference, with corresponding prestored values stored for thiscombination in the table memory and, on the basis of this comparison,that correction value X_(K,i) is read out, thus used by the evaluationelectronics 2 for the further calculations, which corresponds to theprestored value having the closest match with the instantaneouscombination. The table memory can be a programmable, fixed-value memory,thus a FPGA (field programmable gate array), an EPROM or an EEPROM. Theuse of such a table memory has, among others, the advantage that thecorrection value X_(K) is available during runtime very quicklyfollowing calculation of the intermediate values X₁, X₂. Moreover, thecorrection values X_(K,i) entered in the table memory can bepredetermined very accurately, e.g. based on the Eqs. (2), (3) and/or(4) and making use of the method of least squares.

As can be appreciated, without more, from the above presentation, acorrection of the initial measured value X′_(x) can be carried out, onthe one hand, using few correction factors which are very easy todetermine. Also, the correction can be performed using the twointermediate values X₁, X₂ with a computing effort, which is quite smallin comparison to the more complexly developed computing methods knownfrom the state of the art. An additional advantage of the invention isto be seen in the fact that at least some of the described correctionfactors can be generated, without more, from the flow parametersdetermined, for example, by means of conventional Coriolis mass flowmeasuring devices, especially the measured density and/or the—hereprovisionally—measured mass flow rate, and/or from the operationalparameters usually directly measured in the operation of Coriolis massflow measuring devices, especially the measured oscillation amplitudes,oscillation frequencies and/or derived from the exciter current, and,consequently without noticeable increase of the circuit and measurementcomplexity.

16. An inline measuring device for the measurement of at least onephysical, measured quantity of a medium guided in a pipeline, saidinline measuring device comprising: a vibratory-type measurement pickup;and measuring device electronics electrically coupled with saidvibratory-type measurement pickup, wherein said measurement pickupincludes: at least one essentially straight measuring tube inserted intothe course of the pipeline, said measuring tube serving to guide themedium to be measured; an exciter arrangement acting on said at leastone measuring tube for causing said at least one measuring tube tovibrate, said exciter arrangement causing the measuring tube to vibrateat least at times with lateral bending oscillations, and to vibrate atleast at times with torsional oscillations about an imaginary measuringtube longitudinal axis essentially aligned with said at least onemeasuring tube; and a sensor arrangement for registering vibrations ofsaid at least one measuring tube and for delivering at least oneoscillation measurement signal representing oscillations of saidmeasuring tube; further wherein: said measuring device electronicsdelivers, at least at times, an exciter current driving the exciterarrangement, and determines a first intermediate value, whichcorresponds to a lateral current component of the exciter currentserving to maintain lateral oscillations of the measuring tube, and asecond intermediate value, which corresponds to a torsional currentcomponent of the exciter current serving to maintain torsionaloscillations of the measuring tube; and said measuring deviceelectronics uses said first and the second intermediate values forgenerating at least one measured value, which represents at least onephysical quantity of the medium to be measured.
 17. The inline measuringdevice as claimed in claim 16, wherein: said measuring deviceelectronics uses said at least one oscillation measurement signal forgenerating at least one measured value.
 18. The inline measuring deviceas claimed in claim 16, wherein: said sensor arrangement delivers atleast one first oscillation measurement signal, which represents, atleast in part, inlet-end lateral oscillations of said at least onemeasuring tube, and at least one second oscillation measurement signal,which represents, at least in part, outlet-end lateral oscillations ofsaid at least one measuring tube.
 19. The inline measuring device asclaimed in claim 18, wherein: said measuring device electronics usessaid first and second oscillation measurement signals for generatingsaid at least one measured value.
 20. The inline measuring device asclaimed in claim 19, wherein: said at least one measured valuerepresents a mass flow rate of the medium flowing in said at least onemeasuring tube.
 21. The inline measuring device as claimed in claim 16,wherein: said least one measured value represents a density of themedium flowing in said at least one measuring tube.
 22. The inlinemeasuring device as claimed in claim 16, wherein: said at least onemeasured value represents a viscosity of the medium flowing in said atleast one measuring tube.
 23. The inline measuring device as claimed inclaim 16, wherein: said at least one measured value represents a massflow rate of the medium flowing in said at least one measuring tube. 24.An inline measuring device for the measurement of at least one physical,measured quantity x of a medium guided in a pipeline, said inlinemeasuring device comprising: a vibratory-type measurement pickup; andmeasuring device electronics electrically coupled with saidvibratory-type measurement pickup, wherein said measurement pickupincludes: at least one essentially straight measuring tube inserted intothe course of the pipeline, said measuring tube serving to guide themedium to be measured; an exciter arrangement acting on said at leastone measuring tube for causing said at least one measuring tube tovibrate, said exciter arrangement causing the measuring tube to vibrateat least at times with lateral bending oscillations, and to vibrate atleast at times with torsional oscillations about an imaginary measuringtube longitudinal axis essentially aligned with said at least onemeasuring tube; and a sensor arrangement for registering vibrations ofsaid at least one measuring tube and for delivering at least oneoscillation measurement signal representing oscillations of saidmeasuring tube; further wherein: said measuring device electronicsdelivers, at least at times, an exciter current driving the exciterarrangement, and determines a first intermediate value, whichcorresponds to a damping of lateral oscillations of the measuring tube,and a second intermediate value, which corresponds to a damping oftorsional oscillations of the measuring tube; and said measuring deviceelectronics uses said first and the second intermediate values forgenerating at least one measured value, which represents at least onephysical quantity of the medium to be measured.
 25. The inline measuringdevice as claimed in claim 24, wherein: said measuring deviceelectronics uses said at least one oscillation measurement signal forgenerating at least one measured value.
 26. The inline measuring deviceas claimed in claim 24, wherein: said sensor arrangement delivers atleast one first oscillation measurement signal, which represents, atleast in part, inlet-end lateral oscillations of said at least onemeasuring tube, and at least one second oscillation measurement signal,which represents, at least in part, outlet-end lateral oscillations ofsaid at least one measuring tube.
 27. The inline measuring device asclaimed in claim 26, wherein: said measuring device electronics usessaid first and second oscillation measurement signals for generatingsaid at least one measured value.
 28. The inline measuring device asclaimed in claim 27, wherein: said at least one measured valuerepresents a mass flow rate of the medium flowing in said at least onemeasuring tube.
 29. The inline measuring device as claimed in claim 24,wherein: said at least one measured value represents a density of themedium flowing in said at least one measuring tube.
 30. The inlinemeasuring device as claimed in claim 24, wherein: said at least onemeasured value represents a viscosity of the medium flowing in said atleast one measuring tube.
 31. The inline measuring device as claimed inclaim 24, wherein: said at least one measured value represents a massflow rate of the medium flowing in said at least one measuring tube. 32.A method for measuring a physical, measured quantity of a medium flowingin a pipeline by means of an inline measuring device including avibration-type measurement pickup, and measuring device electronicselectrically coupled with the measurement pickup, said method comprisingthe steps of: allowing the medium to be measured to flow through atleast one essentially straight measuring tube of the measurement pickup,with the measuring tube being in communication with the pipeline;feeding an exciter current into an exciter arrangement mechanicallycoupled with the measuring tube guiding the medium, for causing themeasuring tube to execute mechanical oscillations; causing the measuringtube to execute lateral bending oscillations, and causing the measuringtube to execute torsional oscillations about an imaginary measuring tubelongitudinal axis essentially aligned with said at least one measuringtube; registering vibrations of the measuring tube and producing atleast one oscillation measurement signal representing oscillations ofthe measuring tube; determining a first intermediate value, whichcorresponds to a lateral current component of the exciter currentserving to maintain lateral oscillations of the measuring tube;determining a second intermediate value, which corresponds to atorsional current component of the exciter current serving to maintainthe torsional oscillations of the measuring tube; and using said firstand second intermediate values for producing a measured valuerepresenting said physical, measured quantity.
 33. The method as claimedin claim 32, further comprising a step of: using said at least oneoscillation measurement signal for generating at least one measuredvalue.
 34. The method as claimed in claim 32, further comprising a stepof: delivering a first oscillation measurement signal, which represents,at least in part, inlet-end lateral oscillations of said at least onemeasuring tube.
 35. The method as claimed in claim 34, furthercomprising a step of: delivering a second oscillation measurementsignal, which represents, at least in part, outlet-end lateraloscillations of said at least one measuring tube.
 36. The method asclaimed in claim 35, further comprising a step of: using said first andsecond oscillation measurement signals for generating said at least onemeasured value.
 37. The method as claimed in claim 36, wherein: the atleast one measured value represents a mass flow rate of the mediumflowing in said at least one measuring tube.
 38. The method as claimedin claim 33, wherein: at least one measured value represents a densityof the medium flowing in said at least one measuring tube.
 39. Themethod as claimed in claim 32, wherein: at least one measured valuerepresents a viscosity of the medium flowing in said at least onemeasuring tube.
 40. The method as claimed in claim 32, wherein: at leastone measured value represents a mass flow rate of the medium flowing insaid at least one measuring tube.
 41. A method for measuring a physical,measured quantity of a medium flowing in a pipeline by means of aninline measuring device including a vibration-type measurement pickup,and measuring device electronics electrically coupled with themeasurement pickup, said method comprising the steps of: allowing themedium to be measured to flow through at least one essentially straightmeasuring tube of the measurement pickup, with the measuring tube beingin communication with the pipeline; feeding an exciter current into anexciter arrangement mechanicallycoupled with the measuring tube guidingthe medium, for causing the measuring tube to execute mechanicaloscillations; causing the measuring tube to execute lateral bendingoscillations, and causing the measuring tube to execute torsionaloscillations about an imaginary measuring tube longitudinal axisessentially aligned with said at least one measuring tube; registeringvibrations of the measuring tube and producing at least one oscillationmeasurement signal representing oscillations of the measuring tube;determining a first intermediate value, which corresponds to a dampingof said lateral oscillations of the measuring tube; determining a secondintermediate value, which corresponds to a damping of said torsionaloscillations of the measuring tube; and using said first and secondintermediate values for producing a measured value representing saidphysical, measured quantity.
 42. The method as claimed in claim 41,further comprising a step of: using said at least one oscillationmeasurement signal for generating at least one measured value.
 43. Themethod as claimed in claim 41, further comprising a step of: deliveringa first oscillation measurement signal, which represents, at least inpart, inlet-end lateral oscillations of said at least one measuringtube.
 44. The method as claimed in claim 43, further comprising a stepof: delivering a second oscillation measurement signal, whichrepresents, at least in part, outlet-end lateral oscillations of said atleast one measuring tube.
 45. The method as claimed in claim 44, furthercomprising a step of: using said first and second oscillationmeasurement signals for generating said at least one measured value. 46.The method as claimed in claim 45, wherein: the at least one measuredvalue represents a mass flow rate of the medium flowing in said at leastone measuring tube.
 47. The method as claimed in claim 41, wherein: atleast one measured value represents a density of the medium flowing insaid at least one measuring tube.
 48. The method as claimed in claim 41,wherein: at least one measured value represents a viscosity of themedium flowing in said at least one measuring tube.
 49. The method asclaimed in claim 41, wherein: at least one measured value represents amass flow rate of the medium flowing in said at least one measuringtube.